/*
 * Copyright 2010-2020 Alfresco Software, Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.activiti.core.el.juel.util;

import jakarta.el.ELContext;
import jakarta.el.ELResolver;
import jakarta.el.FunctionMapper;
import jakarta.el.ValueExpression;
import jakarta.el.VariableMapper;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Simple context implementation.
 *
 * @author Christoph Beck
 */
public class SimpleContext extends ELContext {

    static class Functions extends FunctionMapper {

        Map<String, Method> map = Collections.emptyMap();

        @Override
        public Method resolveFunction(String prefix, String localName) {
            return map.get(prefix + ":" + localName);
        }

        public void setFunction(
            String prefix,
            String localName,
            Method method
        ) {
            if (map.isEmpty()) {
                map = new HashMap<String, Method>();
            }
            map.put(prefix + ":" + localName, method);
        }
    }

    static class Variables extends VariableMapper {

        Map<String, ValueExpression> map = Collections.emptyMap();

        @Override
        public ValueExpression resolveVariable(String variable) {
            return map.get(variable);
        }

        @Override
        public ValueExpression setVariable(
            String variable,
            ValueExpression expression
        ) {
            if (map.isEmpty()) {
                map = new HashMap<String, ValueExpression>();
            }
            return map.put(variable, expression);
        }
    }

    private Functions functions;
    private Variables variables;
    private ELResolver resolver;

    /**
     * Create a context.
     */
    public SimpleContext() {
        this(null);
    }

    /**
     * Create a context, use the specified resolver.
     */
    public SimpleContext(ELResolver resolver) {
        this.resolver = resolver;
    }

    /**
     * Define a function.
     */
    public void setFunction(String prefix, String localName, Method method) {
        if (functions == null) {
            functions = new Functions();
        }
        functions.setFunction(prefix, localName, method);
    }

    /**
     * Define a variable.
     */
    public ValueExpression setVariable(
        String name,
        ValueExpression expression
    ) {
        if (variables == null) {
            variables = new Variables();
        }
        return variables.setVariable(name, expression);
    }

    /**
     * Get our function mapper.
     */
    @Override
    public FunctionMapper getFunctionMapper() {
        if (functions == null) {
            functions = new Functions();
        }
        return functions;
    }

    /**
     * Get our variable mapper.
     */
    @Override
    public VariableMapper getVariableMapper() {
        if (variables == null) {
            variables = new Variables();
        }
        return variables;
    }

    /**
     * Get our resolver. Lazy initialize to a {@link SimpleResolver} if necessary.
     */
    @Override
    public ELResolver getELResolver() {
        if (resolver == null) {
            resolver = new SimpleResolver();
        }
        return resolver;
    }

    /**
     * Set our resolver.
     *
     * @param resolver
     */
    public void setELResolver(ELResolver resolver) {
        this.resolver = resolver;
    }
}
